Including interesting content on your Facebook page or in your newsletter is important. Your audience will quickly get bored if all you ever do is hawk your books. What interests do most your readers have? What will they find interesting?
If you don’t know, then there’s a good chance that’s you’re also missing out on venues where you should be marketing and promoting your work. How do you find out? You might try the personal approach and visit the Facebook pages of some of your “fans” who have liked your author page. See what kind of information they’re sharing and the types of activities they enjoy with their friends.